Mixing apparatus for the mixing of a bleaching agent into cellulosic pulp



Nov. 16, 1965 J. c. F. c. RICHTER 3,218,040 MIXING APPARATUS FOR THE MIXING OF A BLEACHING AGENT INTO CELLULOSIC PULP. 7 Filed Aug. 10, 1964 2 sheets sheet 1 INVENTOR.

M 4. KdLfiM MLQA MM Nov. 16, 1965 J c F. c. RICHTER 3,218,040

MIXING APPARATLIS FOR THE MIXING OF A BLEACHING AGENT INTO CELLULOSIC PULP Filed Aug. 10, 1964 2 Sheets-Sheet 2 IN V EN TOR.

4X4 5% ML IMW 3,218,040 MIXING APPARATUS FOR THE MIXING OF A BLEACHING AGENT INTO CELLULOSIC PULP Johan C. F. C. Richter, St. Jean Cap Ferret, France, assiguor to Aktiebolaget Kamyr, Karlstad, Sweden, a company of Sweden Filed Aug. 10, 1964, Ser. No. 388,461 Claims priority, application Sweden, Aug. 12, 1963, 8,778/63 8 Claims. (Cl. 259-23) The present invention relates to an apparatus for mixing a bleaching agent into cellulosic pulp, particularly high'consistency pulp having a dry content of, e.g., 8 to 20%. The mixing apparatus of the invention is of the type comprising a casing with an agitating member enclosed therein and provided with vanes or the like, a stationary, radially distributed inlet for the bleaching agent being located near the agitating member.

The principal object of the invention is to provide an apparatus for obtaining a uniform mixture of bleaching agent and pulp. A more specific object of the invention is to provide means for mixing by distributing the bleaching agent in a column of pulp fed through the casing, along a continuous helical surface or path. Other objects will also be hereinafter apparent.

Broadly stated, the objects of the invention are realized by the provision of an apparatus which comprises a casing, agitating means including a rotatable shaft with mixing vanes mounted thereon and positioned within the casing, a stationary, radially positioned inlet for supplying bleaching agent to the casing located adjacent the agitating means, the casing including an end wall transverse to the shaft and having an opening therein for supply of pulp to the casing, the end wall forming a helical surface which extends substantially a complete revolution around the shaft of the agitating means, and a supply conduit connected to the end wall eccentrically to the shaft and communicaiing with the end wall opening, the mixing vanes being positioned to sweep over the opening and carry pulp supplied thcrethrough in a circular path along the helical surface formed by the end wall whereby bleaching agent from the inlet is distributed into the pulp and the latter is advanced axially.

The invention is more fully described below with reference to the accompanying drawings wherein:

FIGURE 1 is a vertical cross-sectional view of a preferred embodiment of the mixing apparatus;

FIGURE 2 is a horizontal cross-sectional view taken along the line IlII in FIGURE 1; and

FIGURES 3 and 4 are corresponding sectional views of a modified embodiment.

Referring to FIGURES 1 and 2, the'mixing apparatus of the invention is placed at the bottom 11 of a bleach tower (shown in part only) to which cellulosic pulp is supplied through a conduit 13. A conventional bleaching agent meant to react with the pulp in the tower is supplied through a conduit 15 (FIGURE 2). In order to obtain uniform bleaching, it is important that the bleaching agent be evenly distributed into the pulp before it enters the tower, because usually no further mixing takes place in the tower.

The mixing apparatus comprises a rotary agitating member 17 and a casing enclosing the same and constituting a cylindrical shell 19 which at its upper part merges into the conical bottom part 11 of the bleach tower. An end wall 21 forms the bottom of the casing; In the upward direction, the casing is in completely open communication with the bleach tower.

The agitating member 17 is attached to a vertical shaft 23 coaxial to the cylindrical shell 19 of the casing and Patented Nov. 16, 1965 ice - journalled in bearings 25, 27. The shaft extends through connection 13 is located laterally of shaft 23 and forms an orifice 31 of approximately circular configuration which in the radial direction takes up essentially the entire space available between the cylindrical shell 19 and the stuffing box 29.

The agitating members 17 comprises a hub 33 attached to the upper end of the shaft 23, a lower series of vanes or blades 35 and an upper series of vanes or blades 37. Preferably, the vanes 35 are set vertically and in radial planes, whereas the vanes 37 may be inclined or twisted so that they have a certain advancing action upon the pulp in addition to agitating the same.

At its upper side, the end wall 21 is provided with concentric annular ledges 39, 41 of a rectangular cross-section rising above the plane bottom surface 43 of the end wall. These ledges have their minimum height at one side of the orifice 31 and rise gradually so that they reach their maximum height at their open ends near the opposite side of the orifice 31. Thus, they form inclined planes constituting somewhat less than one complete revolution of a helical surface having the shaft of the agitating memher as its axis and a horizontal line at right angles thereto as its generatrix.

The conduit 15 for the supply of the bleaching agent is connected to an outlet nozzle 45 which is approximately radially directed and which is located in the end wall 21 near that edge of the orifice 31 where the ledges 39, 41 have their minimum height. The nozzle 45 extends from the cylindrical shell 19 as far as possiible towards the center and its orifice or outlet aperture is arranged to discharge the bleaching agent in a proportion increasing with the distance from the shaft in order thereby to distribute the bleaching agent evenly over the cross-sectional area of the pulp column moving upwardly in the bleach tower.

The vanes of the agitating member are provided in their lower edges with square projections or dents 47 and intermediate recesses 49. The projections 47 extend between the ledges 39, 41 of the end wall of the casing and move closely to its plane surface 43. The recesses 49 run at a varying distance from and above the upper helical surfaces of the ledges.

In operation, the pulp rising through the orifice 31 is deviated into a circular path by the vanes 35 of the rotary member, the bleaching agent being added to the pulp as the same passes the nozzle 45. During its continued circular movement, the pulp slides upon the evenly rising ledges 39, 41 and is thereby advanced axially upwards, so that when the vanes 35 move above the orifice 31 anew, they will catch a new batch of the pulp. During each revolution of the agitating member, a portion of the pulp will be circulated in sliding contact with the plane parts 43 of the end wall of the casing and will not be advanced axially. Therefore, a displacement in the axial direction will take place between different portions of pulp supplied simultaneously through the orifice 31. However, due to mingling above the orifice 31, such pulp as has not been axially advanced during its first circular run, will sooner or later be brought above the inclined planes of the ledges and advanced upwardly, too.

The modification shown in FIGURES 3 and 4 corresponds closely to the embodiment just described, the same reference numerals being used for corresponding details. The end wall 21 of the casing is made plane and without ledges and, therefore, forms almost a complete turn of a helical surface 44 extending between the sides tically upwards through the casing 19. The mixing between layers on opposite sides of the helical surface is effected by a series of curved blades 38 which are attached to the bottom 11 0f the bleachtower and which extend tangentially and radially inwards, their lower edge being located closely to the surface described by the upper edges 50 of the rotary vanes 35.

It will be appreciated that various modifications may be made in the invention described above. For example, the mixing apparatus of the invention may also be designed as a separate unit connected to the bleach tower by a tube conduit. Additionally, if desired, the mixing apparatus maybe arranged with its shaft extending horizontally. Other modifications are also contemplated as coming within the scope of the invention as defined in the claims appended hereto wherein:

I claim:

1. Apparatus for mixing bleaching agent into cellulosic pulp, particularly pulp of high consistency, which COrnpriseS a casing, agitating means including a rotatable shaft with mixing vanes mounted thereon and positioned within said casing, a stationary, radially positioned inlet for supplying bleaching agent to said casing located adjacent said agitating means, said casingincluding an end wall transverse to said shaft and having an opening therein for supply of pulp to said casing, said end wall having upon it a helical surface which extendssubstantially a complete revolution around the shaft of the agitating means, and a supply conduit connected to said end wall eccentrically to said shaft and communicating with said end wall opening, said mixing vanes being positioned to sweep over said opening and carry pulp supplied therethrough in a circular path along the helical surface formed upon the end wall whereby bleaching agent from said inlet is diestributed into said pulp and the latter is advanced axially.

2. Mixing apparatus according to claim 1, wherein said end wall is provided with a plane bottom surface portion with at least one concentric annular ledge having a helical upper surface projecting above said bottom surface portion.

3. Mixing apparatus according to claim 2, wherein said plane bottom surface portion has at least two concentric annular ledges and said vanes include projections which extend down between said ledges and run close to said plane bottom surface portion.

4. Mixing apparatus according to claim l including stationary blades fixed to said casing, wherein said stationary blades are arcuate and extend tangentially and radially toward the center of the casing.

5. In combination with a bleaching tower, a casing fixed to the bottom of said tower and in open communication therewith, said casingcomprisin g' (l) a vertical cylindrical shell which defines the lateral extent of said casing and is fixed at its upper end to the bottom of said tower, and (2) an end wall constituting the bottom of said casing and including an opening therein for the supply of pulp to said casing, said end wall having a plane surface with a series of annular ledges thereon of essentially rectangular cross-section projecting into said casing at a height varying from a minimum adjacent one side of said end wall opening to a maximum on the other side of said opening thereby forming inclined planes constituting almost a complete revolution of a helical surface having the shaft of the agitating member as its axis and a horizontal line at right angles thereto as its generatrix; mixing means within said casing, said means including a vertical rotatable shaft extending centrally through said end wall with mixing vanes fixed thereto and rotatable therewith within said casing; the bottom edges of said mixing vanes being provided, with alternating recesses and projections, the latter extending between the ledges in said end wall and terminating close to the plane surface of said end wall; and means for adding bleaching agent to said casing and radially thereof at a point just beyond the opening in said end wall adjacent said vanes.

6. Apparatus according to claim 5 wherein said opening in the end wall for supply of pulp extends'radially from a point adjacent said cylindrical shell to a point close to the center of said end wall.

7. Mixing apparatus according to claim 5 wherein said mixing means includes an upper and lower series of vanes, the lower vanes being mounted vertically in radial planes and the upper vanes being inclined so as to simultaneously advance and agitate the pulp.

8. In combination with a bleaching tower, a casing fixed to the bottom of said tower and in open communication therewith, said casing comprising (1) a vertical shell which defines the lateral extent of said casing andis joined at its upper edge to the bottom of said tower and (2) an end wall constituting the bottom of said casing and having.

an opening therein for the supply of pulp to said casing, said end wall having a plane surface so inclined as to form substantially one turn of a helical surface from one side of said opening to the other; mixing means within said v casing, said means including a vertical rotatable shaft extending centrally through said end wall with mixing vanes fixed to said shaft and rotatable therewith within said casing, the lower edges of said vanes being straight and reaching down to said helical surface of the end wall only at the highest part thereof just prior to said opening; and means for adding bleaching agent to said casing and radially thereof at a point adjacent said vanes and just beyond the opening in said end wall.

References Cited by the Examiner UNITED STATES PATENTS 2,478,893 8/1949 Brant 259-66 X 2,764,011 9/l956 Richter 68-l8l WALTER A. SCHEEL, Primary Examiner.

CHARLES A. WILLMUTH, Examiner. 

1. APPARATUS FOR MIXING BLEACHING AGENT INTO CELLULOSIC PULP, PARTICULARLY PULP OF HIGH CONSISTENCY, WHICH COMPRISES A CASING, AGITATING MEANS INCLUDING A ROTATABLE SHAFT WITH MIXING VANES MOUNTED THEREON AND POSITIONED WITHIN SAID CASING, A STATIONARY, RADIALLY POSITIONED INLET FOR SUPPLYING BLEACHING AGENT TO SAID CASING LOCATED ADJACENT SAID AGITATING MEANS, SAID CASING INCLUDING AN END WALL TRANSVERSE TO SAID SHAFT AND HAVING AN OPENING THEREIN FOR SUPPLY OF PULP TO SAID CASING, SAID END WALL HAVING UPON IT A HELICAL SURFACE WHICH EXTENDS SUBSTANTIALLY A COMPLETE REVOLUTION AROUND THE SHAFT OF THE AGITATING MEANS, AND A SUPPLY CONDUIT CONNECTED TO SAID END WALL ECCENTRICALLY TO SAID SHAFT AND COMMUNICATING WITH SAID END WALL OPENING, SAID MIXING VANES BEING POSITIONED TO SWEEP OVER SAID OPENING AND CARRY PULP SUPPLIED THERETHROUGH IN A CIRCULAR PATH ALONG THE HELICAL SURFACE FORMED UPON THE END WALL WHEREBY BLEACHING AGENT FROM SAID INLET IS DISTRIBUTED INTO SAID PULP AND THE LATTER IS ADVANCED AXIALLY. 